For buildings of normal earthquake-resistant construction, it is essential to provide their structural frame with sufficient rigidity and strength horizontally and vertically, ensuring a uniform distribution of rigidity and strength in the plane. To this end, it is typical that those buildings adopt the same type of construction and structural system. On the other hand, in buildings of general base-isolation construction, their upper structure, which is supported by a base isolation layer, undergoes lessened seismic forces and therefore is able to tolerate concentration of rigidity and strength. This makes them available for construction with any types of structural systems, which in turn allows new structural planning realizing a greater freedom in architectural design; the same type of construction and structural system for the upper structure is generally adopted. In contrast, when a high-rise building is provided with an isolation layer in an intermediate level, its upper structure, which is placed above the isolation layer, has high seismic resistance as a seismic isolation structure. And a mass damper effect contributes to decrease in seismic responses in the lower structure, ensuring high seismic resistance of a building. This paper describes the physical properties of a seismic isolation layer system which is built at an middle-story of a building. It also introduce buildings by which potentials for new architectural planning are proposed through the use of this system.
N. Z. parliament buildings seismic protection by base isolation
